A while ago we announced our plan to migrate to the Web Extensions platform. With the current Firefox nightly builds being incompatible to classic add-ons already, we need to move a bit prematurely. So starting with Adblock Plus 2.99.0.1814 development build, our development builds will be using the Web Extensions platform. If you are on Firefox 57, make sure to install the latest Adblock Plus development build and it will be working again.

There are some drawbacks here. Most notably, the user interface will be more limited than what you are used to. The work improving the options page is almost done and should land soon, other parts of the user interface will follow. Still, disabling individual filters won’t be back for a while, which is why we are re-enabling any filters you might have disabled in subscriptions. Disabled custom filters will be automatically replaced by comments. We also remove any automatic backups (not the manual backups) you might have, these degrade Firefox performance and currently cannot be recovered anyway.

The other important drawback is very limited Android support. There is ongoing work both on our and Mozilla’s side here, so things should improve very soon.

As of Firefox 57, classic extensions such as the current Adblock Plus for Firefox will no longer load and only Web Extensions will be allowed to continue working. In order to prepare for the transition, starting with Adblock Plus 2.8.2.4244 development build we will use Web Extensions for data storage. Any existing data (this includes both current filters/subscriptions and automatic backups) will be taken over automatically and ideally there should be no visible changes at this point. However, the data will no longer be stored in the adblockplus/patterns.ini file of your Firefox profile but rather in the browser-extension-data/{d10d0bf8-f5b5-c8b4-a8b2-2b9879e08c5d}/storage.json file.

Please tell us about any data loss issues you encounter after this change. We are moving towards releasing Adblock Plus 2.9 which will start data migration for our entire user base. Note that the format of the Web Extensions storage is still supposed to change which will hopefully make it more robust and performant.

Traditionally, element hiding on Firefox worked quite differently from all other platforms supported by Adblock Plus. Rather than decide on the filters for each website individually, all element hiding rules would be written into a single elemhide.css stylesheet file that would apply to all websites unconditionally. This approach had a few disadvantages:

The global stylesheet could not consider exceptions, such as websites where a particular rule should not apply — we had to implement a complicated mechanism to make sure that the rule didn’t have any effect in such cases, and on some websites there still were side-effects.

Changing a single element hiding rule caused the global stylesheet to apply again to all open tabs, this could cause significant delays.

With multiprocess Firefox coming up and sandboxing enabled on some platforms, we could no longer rely on being able to access that file.

Luckily, Firefox implemented better mechanisms to apply stylesheets to documents a while ago and as of Adblock Plus 2.7.3.4206-beta development build we are now taking full advantage of these. We will now make a separate decision for each website, which (if any) element hiding rules should apply. And we don’t sacrifice performance for that because the majority of element hiding rules will go into a preloaded stylesheet with all the rules which apply unconditionally.

There are a few drawbacks here:

New element hiding rules will no longer apply immediately, just like blocking rules they now require the document to be reloaded (can actually be seen as a good thing because consistent). This also affects Element Hiding Helper extension which will need to be updated.

We are no longer able to count hits for element hiding exception rules (issue 4509). We simply don’t know any more whether the rule that the exception applies to would have matched anything.

Element hiding rules apply with a slight delay which in theory might cause some ads being shown and then flashing out. In practice, I haven’t seen this yet.

This is a huge change to the inner workings of Adblock Plus and while we tested it quite thoroughly some issues are expected — let us know if you notice any.

Starting with Adblock Plus 1.12.2 for Chrome, Opera and Safari we can block connections initiated via WebSockets on all major platforms (this functionality was available on Firefox since the very start). However, we didn’t have a special type for these requests as these were listed with type “other” instead. The assumption was that the protocol ws:// or wss:// would be sufficient for filter list authors in order to target WebSocket connections specifically. However, we received feedback that this wasn’t the case.

So with the current development builds (Adblock Plus 2.7.3.4202 for Firefox and Adblock Plus 1.12.2.1655 for Google Chrome, Opera and Safari) WebSocket connections are listed with the new type “websocket.” Consequently, filters can be made to target such connections specifically by adding $websocket type option. Existing filters will have to be duplicated for now:

something$websocket
something$other

This syntax will support both new and old Adblock Plus versions as long as the versions without support for the “websocket” type are still common (these will ignore the first filter).

Edit (2016-09-22): This post was originally suggesting specifying both websocket and other options on one filter. This approach will not work in Adblock Plus versions without support for the websocket option because filters with unknown options are ignored.

We continued working on improving our support for multi-process Firefox. So far we have still been relying on backwards compatibility code in Firefox which is slow and error-prone. However, starting with Adblock Plus 2.7.0.4123-beta development build that backwards compatibility code no longer applies to Adblock Plus — now we are on our own. As far as I know, all issues have been resolved, with one exception:

This development build is a release candidate for Adblock Plus 2.7.1 which we plan to release on January 19, 2016. Please tell us if you notice any other issues, particularly around Blockable items list and Issue reporter.

Diagnostics extension stopped working with the recent Adblock Plus development builds due to significant architectural changes in the latter. This has been fixed in Diagnostics 1.2.5.245, it is compatible to the Adblock Plus 2.6.13.4090 development build and also to the upcoming Adblock Plus 2.7 release. It is not compatible to older Adblock Plus versions however. We plan to release Diagnostics 1.3 next Tuesday (December 15), on the same day as Adblock Plus 2.7.

Diagnostics had to be changed significantly in order to match the new architecture of Adblock Plus:

The confusing “ignore early returns” checkbox is gone – Diagnostics is no longer able to track low-level actions, so it generally cannot detect low-level calls that aren’t being forwarded to the upper level. However, there are relatively few such cases remaining in Adblock Plus now.

The columns Context, Document and Additional have been removed as well – this kind of low-level context information is no longer available to Diagnostics (and neither to Adblock Plus when it is making decisions).

On the other hand, the Request origin data has been extended. The tooltip will now show the entire frame hierarchy for a request, not only the location of the frame immediately responsible.

There is also a new column called Private. This one will indicate whether a request is associated with a private browsing window.

The Type column will no longer attempt to localize the type, instead the internal type identifier will be displayed (corresponds with filter options).

Firefox is switching to a multi-process architecture, it might be switched on by default once Firefox 45 is released. The current Adblock Plus releases mostly work in the multi-process mode but cause slowdowns and other issues. We’ve known that for a long time, but supporting the new multi-process architecture properly required massive changes to how Adblock Plus works. Today, I am happy to announce that the main part of this work is done and ready to be tested.

The current 2.6.13.4085 development build is a release candidate for Adblock Plus 2.7 which we plan to release on December 15, 2015. The extension core has been split up into two parts: the “parent” part which is loaded only once and the “child” part which is loaded into each Firefox process. This split affects almost all of the Adblock Plus functionality, so please report any issues you notice – both with multi-process enabled and without it.

There is a number of known issues:

Element hiding functionality isn’t working on Mac OS X when multi-process is enabled (bug 1187099). Given the lack of progress on Mozilla’s side, we will likely have to come up with a workaround, not for this release however.

Issue reporter hangs up when multi-process is enabled (issue 2809), we will address this issue in the next release.

Selection in the list of blockable items isn’t remembered reliably when multi-process is enabled (issue 3259), we will address this issue in the next release.

Diagnostics for Adblock Plus is broken (issue 3225). We should be able to address this before Adblock Plus 2.7 is released.

Multi-process Firefox is coming, and many people are already testing it with the Firefox nightly builds as well as Firefox Developer Edition. Mozilla went out of their way to make sure that most extensions continue to work unchanged but very often things break nevertheless. So recently Element Hiding Helper’s integration with the Inspector tool broke in Firefox 42 because the Inspector tool was made aware of multiple processes and functionality that Element Hiding Helper relied on went away.

Starting with Element Hiding Helper 1.3.2.497 this issue is resolved. Fixing it required extensive changes to the entire functionality of Element Hiding Helper, not just the Inspector integration. So we would appreciate your help testing Element Hiding Helper both in multi-process Firefox and in the “old” single-process setup.